Transition metal-catalyzed reactions which form carbon-carbon bonds have become an important tool in synthetic organic chemistry. One example is transition metal-catalyzed olefin metathesis, which has been shown to be useful in the synthesis of high molecular weight polymers, pharmaceuticals, and other materials. Olefin metathesis may be defined conceptually as a mutual exchange of alkylidene units between two olefins involving both the formation and cleavage of carbon-carbon double bonds, i.e., via [2+2] cycloadditions between an M=C center and a carbon-carbon double bond. Metal alkylidene complexes including ruthenium and molybdenum alkylidene complexes have been shown to perform olefin metathesis in the presence of a variety of functional groups. However, in many cases, multi-step syntheses are required to generate the catalyst compositions.
In some applications, variation of the substituents and/or ligands of the catalyst may greatly affect the performance of the catalyst. For example, in asymmetric olefin metathesis, the stereoselectivity of a catalyst may be largely affected by the steric size and/or electronic properties of, for example, ligands bound to the metal center of the catalyst. Thus, the availability of a wide variety of catalysts, each having different combinations of ligands and/or substitutents, may be advantageous in optimizing catalysts and/or reactions conditions for a particular chemical reaction. However, using methods currently known in the art, the synthesis and isolation of many different catalyst compositions may be impractical. In some cases, the substitution or replacement of ligands bound to an organometallic catalyst may occur slowly and/or incompletely, or not all. In other cases, the synthesis of organometallic catalysts may occur with poor yield due to the occurrence of side reactions. For example, the syntheses of metal alkylidene complexes for olefin metathesis may often result in low yields due to competitive side reactions including deprotonation of the alkylidene.
Accordingly, improved methods are needed.